Triple concentric eyewalls formation in Typhoon Usagi 2013

Triple concentric eyewalls formation in Typhoon Usagi (2013): observation and simulation Simon(Su) Liu, Fuqing Zhang

Concentric Eyewall Replacement Cycle (ERC) Houze et al. 2007 Primary Eyewall Secondary Eyewall • Procedure: • 1. Outer rainbands may strengthen and organized into a convective ring surrounding the inner eyewall • 2 Outer eyewall contract and ‘chock’ inner eyewall • 3. Outer eyewall replace inner one Why important? ERC connect with TC intensity change

Backgroud: Statistic of Concentric Eyewalls (CE) • Most of Intense TC has CE structure Kuo et al. 2009 • Half the CE happen in TC intensity peak • Compare to No-CE TC, CE has higher intensity for longer duration

Concentric Eyewall formation theory-Still under research • Potential Vorticity generation • Vortex Rossby wave • Formation of unbalanced supergradient wind • 2 D vortex interactions • … Here comes more interesting phenomena -Triple eyewall

Triple Eyewall Observation-aircraft measure Hurricane Frances 2004 Sitkowski et al. 2011 Hurricane Juliette 2001 Mc. Noldy et al. 2004 No evolution or detail structure

Doppler Observation of Usagi 2013 Zhao et al. 2016

Structure of Eyewalls • Both secondary and tertiary eyewall contract with time • Both moats dominate with downdraft Questions: 1. What the role of tertiary eyewall? 2. Why inner eyewall did not dissipate after secondary eyewall formation? Zhao et al. 2016

Initial Run • 3 domains • 27 km/9 km/3 km • Domain 2 and 3 present moving • No Data Assimilation • Future Plan: • Get best initial run (track) • Assimilation doppler velocity to see if triple eyewall could be simulate • …

Thanks! Questions?